The following background discussion is not an admission that anything discussed below is citable as prior art or common general knowledge. The documents listed below are incorporated herein in their entirety by this reference to them.
There is a growing popularity in the use of beverage capsules in beverage preparing machines for preparing individual servings of a desired beverage. One example of a beverage capsule adapted for preparing a beverage in a beverage preparing machine is disclosed in published PCT patent application WO 2010/085824. This capsule includes a body having a filter device disposed at the base. An extractable substance in powder form, in particular a coffee powder, is disposed in the capsule between the filter device and the capsule lid. The filter device has a planar filter surface that defines a plurality of openings. The openings have a diameter of 0.4 millimeters on the side of the filter device that faces the coffee powder. The openings maintain this diameter and have a cylindrical cross section through a portion of the thickness of the filter device and then widen conically at an angle of approximately 40 degrees so that the size of openings on the side facing the base of the capsule is larger than the size of the openings facing the coffee powder. This is provided to facilitate flow-through of liquid under a high pressure and reduce the risk of blockage of the openings by the coffee powder.
High pressure beverage preparing machines are primarily designed for preparing espresso style beverages that include a crema (foam). Crema is very desirable for espresso style beverages and is an important feature for authenticity of such beverages.
Traditional espresso is prepared with a manual or semi-automatic espresso machine in which the coffee beans are ground to a desired mean particulate size of typically 200-300 microns and “hand tamped” with a tamper. Such manual or semi-automatic espresso machines are noted for producing a thick rich crema.
Many modern high pressure fully automatic beverage preparing machines that utilize single serve beverage capsules are designed with the intention to replicate the crema produced by hand-tamped espresso machines with the intention of creating an authentic espresso style beverage without the effort of hand tamping. This desirable crema is composed mostly of foam and tiny bubbles. The foam and bubbles are principally created through the creation of turbulence and high pressure within the beverage capsule during the preparation process. For this reason modern high pressure fully automatic beverage preparing machines have brewing chambers and dispensing systems designed to produce turbulence as the extracted coffee passes through the filtering and dispensing system. The capsules often have openings in the filtering media which are very small and with sharp or abrupt entrance and exit holes which increase turbulence in the stream of the coffee extracting and dispensing system.
Some individuals prefer beverages that more closely resemble a North American drip-style beverage in appearance and taste. The North American drip-style beverage is characterized by a lighter beverage color and strength and minimal or no foam, bubbles or crema. It is desirable that such beverages may be prepared in the same high pressure fully automatic beverage preparing machines that are used for preparing espresso style beverages with crema so that a single machine may serve a variety of beverage tastes.
One example of a beverage capsule adapted for preparing a North American drip-style coffee in a high pressure fully automatic beverage preparing machine is disclosed in U.S. Pat. No. 7,552,672. This capsule includes a body having an aperture defined in the base that is covered by a seal that may be removed by the user or punctured by the machine. A filter element is disposed at the base of the capsule to separate the coffee powder in the capsule from the aperture. The filter element includes a plurality of apertures that are adapted to allow liquid to pass through the filter element while preventing passage of undissolved coffee grounds. The coffee powder is relatively coarsely ground with the arithmetic mean diameter of the particles being between 400 to 600 microns.
A problem with the capsule disclosed in the '672 patent is that the resulting coffee maintains some crema and does not sufficiently resemble a North American drip-style beverage in appearance and taste.
Another example of a beverage capsule adapted for preparing a North American drip-style coffee in a high pressure fully automatic beverage preparing machine is disclosed in FIG. 7 of U.S. Pat. No. 7,685,930. This capsule includes a body having a permeable retaining wall that is supported by a support plate proximate to the base of the capsule. The retaining wall has a plurality of openings or pores enabling the flow of beverage there through. The retaining wall may be made of paper or fibres or other materials. The support plate may be in the form of a grid or an apertured rigid corrugated plate that allows beverage to flow through at relatively low pressures so that the production of foam is minimized or prevented.
A problem with the capsule disclosed in the '930 patent is that it includes an internal shoulder to which the “permeable retaining wall” is welded. This internal shoulder restricts the cross-sectional area available for the filtering element. Furthermore, welding a filter to an internal shoulder is difficult to accomplish, which increases the cost and complexity of the filling line and increases the risk of quality issues arising due to improper capsule assembly.
Another example of a beverage capsule adapted for preparing a North American drip-style coffee in a high pressure fully automatic beverage preparing machine is disclosed in published US patent application 2007/0148290. This capsule includes a body having a screening device with large-surface-area cutouts separated by radial ribs. A planar textile fabric which serves as a filter is disposed within the capsule between the beverage ingredients and the cutouts. The screening device is spaced from the base of the capsule by an annular structure having a narrower diameter than the screening device. The annular structure includes a plurality of through openings arranged generally perpendicular to the base of the capsule for allowing the passage of beverage from an outer region below the screening device to an inner region below the screening device. The capsule further includes an opening defined in the base of the capsule that is sealed by a sheet material. The opening is penetrated during use of the capsule by the beverage preparing machine to allow beverage to flow through the opening into a user's cup.
A problem with the capsule disclosed in the '290 application is that the support structure includes a conical protuberance, which necessitates that the planar textile fabric be cut into an annular structure. This is difficult to accomplish, which increases the cost and complexity of the machine for cutting the fabric and assembling the fabric to the support structure. It also increases the risk of quality issues arising due to improper assembly of the fabric structure. The small piece that is punched out of the center of the fabric also becomes a potential source of contamination should it not be properly removed and end up under the disk in the final capsule assembly. A further problem with this capsule is that it requires an annular structure with through-openings underneath the fabric. This structure can restrict the beverage flow and increase turbulence, potentially leading to increased levels of crema in the finished beverage.
It is desirable that a beverage capsule be developed for preparing North American drip-styled beverages in beverage preparing machines that improves upon existing beverage capsules.